With the development of low-grade, small, low-power consuming, low-priced global positioning system (GPS) receivers, GPS receivers have mainly been used as positioning sensors in a commercial vehicle navigation system, and a location-based service (LBS) provides navigation information such as a location, a speed, and the like, and road guidance, notification of a dangerous area, and the like, for users by matching location information of a vehicle obtained through a GPS receiver to a digital map.
However, when a GPS signal is completely or partially blocked in a tunnel, an underground parking lot, a downtown area, and the like, a GPS receiver cannot provide accurate location information.
Thus, in order to provide positioning information without discontinuation, a dead reckoning (DR) system including a speedometer, a geomagnetic sensor, an inertial sensor, and the like, may be coupled to a GPS receiver to configure a DR/GPS complex navigation system.
Such a DR/GPS complex navigation system may be variously configured depending on the forms of DR, coupling schemes, and coupled filters.
Here, A Kalman filter has mostly been used as a coupled filter, and an extended Kalman filter (EKF) is used in order to apply a Kalman filter employed in a linear system to a DR/GPS complex navigation system as a nonlinear system.
GPS reception data is time-delayed data, relative to other sensor data input at the same time, and thus, if GPS reception data and DR data are joined without considering such characteristics of GPS reception data, performance of estimating a location may inevitably be degraded.